Voltage-current converter and voltage controlled oscillator
View Patent ↗An exemplary aspect of an embodiment of the present invention is a voltage-current converter converting an input voltage input to an input terminal to a current to output the current, the voltage-current converter including a first current generating circuit including an input transistor having a gate connected to the input terminal and generating an output current according to a current flowing in the input transistor, and a second current generating circuit including a transistor having a gate having a potential different from potential of a source and a drain, the second current generating circuit generating a superimposed current according to the current flowing in the transistor to supply the superimposed current to the input transistor.
1. A voltage-current converter converting an input voltage input to an input terminal to a current to output the current, the voltage-current converter comprising:
a first current generating circuit including an input transistor comprising a gate connected to the input terminal and generating an output current according to a current flowing in the input transistor; and
a second current generating circuit including a transistor comprising a gate having a potential different from a potential of a source and a drain, the second current generating circuit generating a superimposed current according to a current flowing in the transistor to supply the superimposed current to the input transistor,
wherein the superimposed current flows between a source and a drain of the input transistor, and
wherein the second current generating circuit generates the superimposed current having a current value which does not relate to an input potential of the input terminal.
2. The voltage-current converter according to claim 1 , wherein the second current generating circuit comprises a constant current circuit generating the superimposed current having a current value equal to a current value flowing in the input transistor except the superimposed current when an input level of the input transistor is in a ground potential.
3. The voltage-current converter according to claim 1 , wherein the transistor in the second current generating circuit is formed on a same substrate as the input transistor and has a size corresponding to a gate length and a gate width of the input transistor.
4. The voltage-current converter according to claim 2 , wherein the transistor in the second current generating circuit is formed on a same substrate as the input transistor and has a size corresponding to a gate length and a gate width of the input transistor.
5. The voltage-current converter according to claim 1 , wherein:
the input transistor is connected to a ground potential or a power supply potential through a first resistance element, and
the transistor is connected to the ground potential or the power supply potential through a second resistance element having same characteristics as the first resistance element.
6. The voltage-current converter according to claim 2 , wherein:
the input transistor is connected to a ground potential or a power supply potential through a first resistance element, and
the transistor is connected to the ground potential or the power supply potential through a second resistance element having same characteristics as the first resistance element.
7. The voltage-current converter according to claim 3 , wherein:
the input transistor is connected to a ground potential or a power supply potential through a first resistance element, and
the transistor is connected to the ground potential or the power supply potential through a second resistance element having same characteristics as the first resistance element.
8. The voltage-current converter according to claim 4 , wherein:
the input transistor is connected to a ground potential or a power supply potential through a first resistance element, and
the transistor is connected to the ground potential or the power supply potential through a second resistance element having same characteristics as the first resistance element.
9. A voltage controlled oscillator, comprising:
a voltage-current converter according to claim 1 ; and
an oscillator oscillating in an oscillation frequency according to an output current from the voltage-current converter.
10. A voltage controlled oscillator, comprising:
a voltage-current converter according to claim 2 ; and
an oscillator oscillating in an oscillation frequency according to an output current from the voltage-current converter.
11. A voltage controlled oscillator, comprising:
a voltage-current converter according to claim 5 ; and
an oscillator oscillating in an oscillation frequency according to an output current from the voltage-current converter.